In This Post
This will be the final post of the AspNet SignalR series. In this post, we will create a controller class that can be used to send messages from a REST WebApi to clients connected to our SignalR hub (via our default.html web page).
Looking Back
In the first three posts of this series (links below), we created an AspNet empty web site with support for SignalR and WebApi. When the default.html page opens, the user is automatically joined to a Hub group called All. The hub responds by returning a list of all users currently joined to the All group and the web page displays that list. We can enter messages into a text box and see those messages displayed in a simple DIV - like a chat application.
Now it's time to look ahead....
Create a New Controller Class
Open your SignalRProjects solution in Visual Studio and right click the the Controllers folder under the MySignalRWebSite project (if you used different names, proceed accordingly). In the right click context menu, select Add >> Web Api Controller Class (v 2.1). Name the class SignalRController.cs.
Controller Class Code
Here is the code for the new controller class:
using System;
using System.Collections.Generic;
using System.Web.Http;
using System.Configuration;
using Microsoft.AspNet.SignalR;
using Newtonsoft.Json;
namespace MySignalRWebSite.Controllers
{
public class SignalRController : ApiController
{
[HttpPost]
[AllowAnonymous]
public void PostHubMessage(HubMessage msg)
{
//this is the object the client web page is expecting
var sendMsg = new
{
groupName = msg.MessageToGroup,
userName = msg.MessageFrom,
message = msg.Message
};
//create the connection to the hub
IHubContext context = GlobalHost.ConnectionManager.GetHubContext<SignalRHub>();
//send the message by calling the client proxy method for all users connected to the group
context.Clients.Group(msg.MessageToGroup).processChatMessage(sendMsg);
}
}
public class HubMessage
{
public string Message { get; set; }
public string MessageFrom { get; set; }
public string MessageToGroup { get; set; }
}
}
You'll notice above that I have, for clarity, deleted the out-of-box template functions from the new class - you don't need to do that if you don't want to, but they are not needed for our purposes.
In place of those methods, we have added the PostHubMessage method. We have also added a simple data class (HubMessage) that defines the payload expected by the action whenever it is called.
There are 3 simple steps here:
- Populate a new object from the incoming data
- Connect to our SignalR Hub
- Use the connection to call the client side processChatMessage proxy function
- The client proxy function will call a local JavaScript function that will in turn display the message
Change GET to POST. Copy the root of the URL from your browser and paste it into the Enter request URL textbox.
Add the following to the root URL you just copied
{
"Message":"Test from the SignalR controller",
"MessageFrom": "SignalR Controller",
"MessageToGroup": "All"
}
- Created a New Solution/Project in Visual Studio
- AspNet Framework, Empty, WebApi
- Downloaded the necessary NuGet packages to support desired functionality
- Created C# classed for to support our SignalR hub
- Startup.cs
- SignalRHub.cs
- Created an HTML page (default.html) with JavaScript to interact with the SignalR Hub
- Created a C# SignalR controller (SignalRController.cs) to interact with connected users
- Tested the API with Postman
